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This invention relates to a filter apparatus and method of its operation, particularly to a pressure filter and method for extracting liquids from difficult-to-filter wet slurry fluids and for producing a substantially-dry filter cake of the solid materials present in such slurry fluids.
In many industrial processes and other applications where a slurry of solids and liquids is produced, it becomes necessary to filter the slurry solids from the liquids so that these materials may be efficiently utilized or, alternatively, disposed in an environmentally-safe manner. To separate the solids from the liquids, a filter apparatus, such as a pressure filter, is often used. Known pressure filters generally include one or more pairs of filter plates capable of relative motion. The inlet plate is adapted for receiving the slurry, while the filtered liquids, called the filtrate, are collected by means of the outlet plate, which also provides the requisite support for a filter medium, positioned between the filter plates. This arrangement permits a filtration chamber to be defined by the inlet plate and the filter medium when the plates are pressed together. In the usual production cycle of such a filter, slurry is introduced into the filtration chamber under pressure through an inlet port, whereby it distributes itself throughout the chamber. After the filtration chamber is filled with slurry, the filter executes a series of programmed operations, namely, washing and/or treating the contents of the chamber in a particular manner, as well as pressurizing the chamber to force the liquids from the slurry through the filter medium, leaving the slurry solids, consolidated in a substantially-dry filter cake, within the chamber. The chamber is then opened, allowing the dry filter cake to be removed therefrom.
Known pressure filters are capable of successfully treating a wide variety of slurries. However, the use of such filters has shown to be impractical for filtering certain difficult-to-filter slurries, such as gluten, kaolin, and pigment slurries, to name a few. Some of these difficult-to-filter slurries are too viscous to achieve uniform distribution throughout a conventional deep filtration chamber, making it difficult to force the liquids from the slurry when the filtration chamber is pressurized. This difficulty arises because any voids existing in the slurry due to non-uniform slurry distribution within the filtration chamber allow pressure to escape from the chamber through the filter medium without driving out the interstitial liquids from the slurry being filtered.
Moreover, certain slurries having non-viscous characteristics have also proven to be difficult to filter, either because they contain fine particles, e.g., fines on the order of 0.5-10 microns, or because they include compressible solids. In both cases, the thickness of a filter cake being formed in a deep filtration chamber of a conventional pressure filter is sufficient to make the cake virtually impermeable to liquids under pressure. As a result, the time required to produce a substantially-dry filter cake for these types of difficult-to-filter slurries drastically increases, making it economically unfeasible to use known pressure filters for treating such slurries.
Thus, a need arises for a pressure-filter apparatus capable of efficiently treating difficult-to-filter slurries, such as the types of slurries described above.
It is also desirable to provide a pressure-filter apparatus that maximizes the available filter area in an apparatus having a multi-chamber configuration.
Furthermore, it is desirable to provide a pressure-filter apparatus that is energy-efficient and is capable of producing a substantially-dry filter cake in a minimum amount of time.
A pressure filter is disclosed. The filter apparatus includes two continuous mating surfaces movable relative each other and a filter medium capable of being disposed therebetween. A surface is provided for supporting the filter medium. This supporting surface is bounded by and is, substantially coplanar with one of the continuous mating surfaces. The filter further includes a shallow inlet cavity, bounded by the other of the continuous mating surfaces, and an inlet distributor in communication with the inlet cavity. When the mating surfaces are pressed together, a shallow filtration chamber is defined by the inlet cavity and the filter medium. The filter apparatus may include a plurality of shallow filtration chambers, constructed as described above.
The advantages of the invention will become apparent after consideration of the ensuing description and the accompanying drawings.